<Page
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

  <Page.Resources>
    <ImageBrush x:Key="SourceImage" ImageSource="Garden.jpg" />
  </Page.Resources>

  <TextBlock 
    Text="ImageBrush"
    FontFamily="Tahoma" 
    FontSize="96" 
    FontWeight="Bold" 
    Foreground="{StaticResource SourceImage}" />

</Page>